Transfer elements and method of making same



' y 6, 1969 D. A. NEWMAN ETAL 3,442,681

TRANSFER ELEMENTS AND METHOD OF MAKING SAME Filed July 20, 1967INVENTORS Douylas f2. Newman 4/!40 T 5ofi/oiz/muer United States Patent3,442,681 TRANSFER ELEMENTS AND METHOD OF MAKING SAME Douglas A. Newman,Glen Cove, and Allan T. Schlotzhauer, Locust Valley, N.Y., assignors toColumbia Ribbon and Carbon Manufacturing Co., Inc., Glen Cove,

N.Y., a corporation of New York Filed July 20, 1967, Ser. No. 654,882Int. Cl. B41c 1/06 U.S. 'Cl. 117--36.4 10 Claims ABSTRACT OF THEDISCLOSURE In the manufacture of pressure-sensitive transfer elements ofthe squeeze-out type, the step of rendering such transfer elementscleaner to the touch and resistant to producing typewriter roller markson the copy sheet which comprises treating the ink-releasing surface ofsuch transfer elements with a layer of a dilute solution of a resincontaining a solid particulate heat-activatable blowing agent, andthereafter applying heat to activate the blowing agent and render saidlayer porous.

This application is a continuation in part of copending application Ser.No. 623,322, filed Mar. 15, 1967.

The present invention relates to the field of the so-called squeeze-outcarbon papers and ribbons on which the transfer layer comprises amicroporous non-transferable resinous structure containing within thepores thereof a pressure-exudable ink comprising an oily vehicle andimaging matter. Such transfer elements are illustrated by United StatesPatents Nos. 2,820,717; 2,944,037; 3,037,879 and 3,117,018, amongothers.

Such known transfer elements have been exceptionally successfulprimarily because of their reusability. The resinous binder is nottransferable and its porosity permits the flowable ink to migrate andreplenish areas from which ink has been transferred. However, while theease of flowability has this advantage, it has the disadvantage thatsome amount of the ink can exude to the copy sheet with which it issuperposed when the sheets are inserted into a typewriter or similarbusiness machine having rollers between which the sheets are compressed.

It is possible to avoid or at least diminish this undesirable offsettingby formulating the ink layer from harder, less pressure-compressibleresins or resin mixtures or by using semi-solid ink vehicles. However,this reduces the pressure-sensitivity of the ink layer so that the typedcopies are not as dense as desired, particularly when interleaved carbonpapers are used to produce a number of copies at one typing.

It is the principal object of the present invention to provide improvedsqueeze-out type transfer elements which are clean to the touch and donot produce roller marks on the copy sheet and which retain a highdegree of pressure-sensitivity so as to produce images of high intensityeven when interleaved to produce several copies at one typing.

Other objects and advantages of this invention will be clear to thoseskilled in the art in the light of the present disclosure including thedrawings, in which:

FIGURE 1 is a diagrammatic illustration of the process of applying thepresent supercoatings; and

FIG. 2 is a diagrammatic cross-section, to an enlarged scale, of atransfer element produced according to the present invention.

The objects and advantages of the present invention are attained bytreating the ink-releasing surface of a squeezeout type resinous inklayer with a liquid wash coating consisting essentially of a dilutesolution of a synthetic thermoplastic resin, incompatible with the inkof the ink layer, dissolved in a volatile organic solvent and havinguniformly dispersed therein a heat-activatable blowing agent whichpreferably is insoluble in said solvent, and then applying heat to firstevaporate the solvent and then cause activation of the blowing agentwhereby the wash coating is rendered porous and permeable by the inkreleased from said ink layer under the effects of imaging pressure.

The porous supercoatings of the present invention function similarly toa resinous screen applied over the inkreleasing layer in that they areuniformly porous to permit exuded ink to flow therethrough under theeffects of imaging pressure, and are sufliciently thick to prevent inkfrom flowing completely therethrough under the efiects of lesserpressures such as those applied by the rollers of a typewriter, printingmachine, adding machine or other business machines. It is possible touse extremely thin wash coats without including a blowing agent sincethe wash coat will shed from the exposed ink pores of the ink layer toleave openings in the wash coat. However, the degree of protectionaiforded by such thin wash coats is limited and the amount of pressureexerted by the rollers of some heavy duty business machines issufiicient to cause the ink to exude through the thin Wash coat andproduce roller marks on the copy paper. Heavier wash coats, free ofblowing agents, seal the ink layer and prevent or retard flow of the inkto the copy sheet and result in the production of images of uneven toneor density.

It has also been found that the wash coating must be free of oilsorother oleaginous materials which are incompatible with the resin ofthe wash coating since such materials separate from the resin to formunpigmented droplets through which the ink of the transfer layer must betransmitted. This results in a dilution of the ink and a reduction inits tone or imaging strength, and a lack of uniformity of imagingstrength over the surface of the transfer element. The inclusion ofpigment in such oil phase overcomes this problem but results in atransfer element which is dirty to the touch and produces roller marksduring use.

The present Wash coating compositions consist essentially of solutionsof from about 5% up to about 20% by weight of a synthetic thermoplasticresin dissolved in a volatile organic solvent which preferably is also asolvent for the resinous binder of the ink layer, the resin beingincompatible with the oily ink vehicle of the ink layer to preventcommingling therewith, and from 0.001% to 1% by Weight of a blowingagent which preferably is insoluble in said organic solid and isactivatable at a temperature at least slightly in excess of theevaporation temperature of said organic solvent. Vinyl resins in generalare preferable and include polyvinyl acetate, vinyl chloride polymersand copolymers with vinyl acetate, polystyrene, polyvinyl butyral,acrylic acid and ester polymers and copolymers such as polymethylmethacrylate, methyl methacrylate-ethyl acrylate copolymers and thelike. Other resins such as the polycarbonates, polyethylene, chlorinatedrubber, butadiene styrene, polyurethanes and the like are also suitable.Preferred volatile organic solvents are methyl ethyl ketone, ethylacetate, acetone, methylene chloride, toluol and the like, dependingupon the solubility of the resin of the wash coat. Of course smallamounts of compatible plasticizers, fillers, colorants or the like maybe included provided that such additives do not interfere with theintended performance of the wash coating.

Blowing agents suitable for use according to the present invention aresolid heat-decomposable materials which evolve a gas such as nitrogen, anitrogen oxide, carbon dioxide or any other harmless vapor. The blowingagent preferably is insoluble in the wash coating solvent and isdispersed uniformly in the wash coating composition in finely dividedparticulate form. Also the blowing agent must be one which isdecomposable at a temperature at least slightly in excess of theevaporation temperature of the volatile slovent with which it is used.Otherwise the blowing agent is activated while the wash coating is stillvery fluid and the pores formed are quickly resealed by the fluid resinbinder material. The solvent must first evaporate, at least to a majorextent, so that the wash coat is no longer fluid. At this point theblowing agent is activated by heat in excess of that amount required forevaporation of the solvent, whereby the blowing agent decompass toliberate a gas which forms an air space within the wash coating. Some ofthe gas breaks through the surface of the wash coat to create surfacespores while the remainder stays within the wash coat in interior poresto form an internal sponge of interconnected pores through which ink canbe freely transmitted.

The selection of blowing agents suitable for use in accordance with thelimitations referred to supra is a matter of choice in view of thenumerous materials available for this purpose. Illustrative materialsare p,p-oxybis (benzenesulfonyl hydrazine) which is available fromNaugatuck Chemical Co. under the trademark Celogen, N,N'dimethyl-N,N-dinitroso terephthalamide, diazoaminobenzene,dinitrosopentamethylene tetramine, and the like. These materials areactivated by temperatures in excess of about 90 C. whereas most volatileorganic solvents evaporate at temperatures well below this temperature.Also, since the wash coat and the ink-releasing layer are resinous, theyare heat-stable and can withstand high temperatures Without any illeffects.

The wash coating is applied to the surface of the ink layer and spreadto form a wet film having a thickness of from about /2 point, applied bymeans of a (zero) doctor blade, up to about 25 points. This is thethickness of the liquid wash coating which consists mainly of thevolatile solvent. The dried wash coating has an approximate thicknessrange in excess of from 5% to 20% the thickness of the wet layer sincethe wet layer contains slightly more than from 5% to 20% solids. Broadlythe dried wash coating may have a thickness ranging from 5% of /2 point(0.0025 mil) up to 20% of 25 points (0.5 mil). The preferred range isfrom 0.1 mil up to 0.3 mil. These are theoretically accurate mean rangesalthough it is recognized that the gas formation within the resin of thewash coating expands the wash coating and increases its thickness at thepeak areas of the dried coating. A point is equal to 0.1 mil and 0.0001inch.

The present wash coatings may be applied in the manner illustrated byFIG. 1 of the drawing. The web of transfer element is expended fromsupply roll 11, over idler roller 12 and against application roller 13which is immersed in vat 14 containing a supply of the wash coatingcomposition. The wash coating is applied to the underside 10a of the webover the squeeze-out ink-releasing layer thereon and is spread to thedesired thickness by means of doctor blade 15. The wet web then passesunder idler roller 16 and through heated air tunnel 17 in whichevaporation of the volatile solvent, activation of the blowing agent andsolidification of the supercoating occurs. The web then passes underidler roller 18 and onto take-up roll 19. The heating tunnel preferablyhas two connected heating chambers, the first of which has a temperaturesulficiently high to evaporate the volatile solvents, from about 50 C.to about 80 C., and the second of which has a temperature above about 90C. to decompase the blowing agent after all or most of the solvent hasbeen evaporated.

The structure of the final transfer element is somewhat uncertain butappears to be as illustrated in FIG. 2 of the drawings. The transferelement has a flexible foundation 20 carrying a microporous squeeze-outtype ink-releasing layer 21 and a non-transferable porous syntheticthermoplastic resin supercoating 24 over said ink-releasing layer. Theink-releasing layer comprises a non-transferable microporous resinousstructure 23 containing droplets 22 of pressure-transferable oily inkwithin the pores thereof. The supercoating has a non-transferable porousresin structure 25 containing open surface pores 26 and interconnectedinterior pores 27 containing the gas liberated by the blowing agent.Thus, while imaging pressure is suflicient to exude the oily ink fromthe ink layer and through the supercoating to a copy sheet, the lesserpressure exerted by the rollers of a business machine is not sufficientto cause the oily ink to exude through the supercoatingj24.

Preferably the solvent used in the wash coat composition is anon-solvent for resin structure 23 of the ink layer so that the porousstructure of the ink layer is not disturbed. Otherwise the applicationof the wash coating is diflicult and the wash coating compositionbecomes contaminated.

The following example illustrates the production of one type of transferelement according to the present invention and should not be consideredlimitative.

A film web of /2 mil. polyethylene terephthalate polyester (Mylar) isfirst coated with a thin layer of polyvinylidene chloride (Saran)dissolved in methyl ethyl ketone to provide a receptive undercoatinghaving a thickness of about 0.1 mil. After evaporation of the solvent,the undercoating is coated with the following ink composition.

Parts by Ingredients: weight Styrene-methyl methacrylate copolymer(Zerlon 150) 12.0 Mineral oil 8.0 Refined rapeseed oil 6.0 Sulfonatedvegetable oil 1.7 Blue toning paste 2.2 Black toner pigment 6.6 Ethylacetate 36.5 Toluol 27.0

The applied ink composition is dried at elevated temperatures to form amicroporous ink layer having a thickness of about 0.6 mil.

As shown in FIG. 1, the transfer element 10 formed as above is passed incontact with an application roller 13 so that the ink layer on side 10ais provided with a layer of the wash coating composition in vat 14 whichis a 10% solution of polyvinyl acetate (Vinylite AYAF) dissolved inmethyl ethyl ketone and containing 0.1 part by weight of Celogen blowingagent. Doctor blade 15 spreads the wash coating to a wet thickness ofabout 10 points (1 mil.). Thereafter the transfer element is heated intunnel 17 to temperatures of about 70 C. and C. to evaporate the methylethyl ketone and toluol and activate the Celogen causing it to liberatenitrogen. The dried polyvinyl acetate structure has a porous structurewith a thickness of between 0.1 and 0.2 mil.

The finished film web is collected on take-up roll 19 for cutting intosheets or ribbons of the desired dimensions. The present invention isprincipally concerned with the production of transfer sheets fortypewriter use and transfer strips or wide ribbons for other businessmachine use.

While pigments such as the carbon black, magnetic iron oxides,particulate dyestuffs and toned pigments having dyes of the desiredcolors precipitated and absorbed on the surface of porous pigments arethe preferred coloring materials, other coloring materials are alsouseful including the substantially colorless color-forming reactivechemicals which form colored reaction products on contact with othercolorless coreactive chemicals present on the copy sheet surface.

It should be understood that the present invention also applies to theproduction of self-supporting ink-releasing microporous layers which areformed on a casting surface and thereafter stripped therefrom in knownmanner. Such transfer elements are preferably coated on both surfaceswith the present wash coatings for complete coverage.

Variations and modifications may be made within the scope of the claimsand portions of the improvements may be used without others.

We claim:

1. The process of producing pressure-sensitive transfer elements of thesqueeze-out type which are clean to the touch and resistant to exudingink under the effects of pressure less than imaging pressure whichcomprises:

(a) producing a pressure-sensitive squeeze-out type ink layer comprisinga pressure non-transferable microporous structure of syntheticthermoplastic resin containing within the pores thereof apressure-exudable ink comprising an oily vehicle and coloring matter;

(b) applying over the ink-releasing surface of said ink layer asupercoating of a dilute solution of a synthetic thermoplastic resin ina volatile organic solvent containing a blowing agent which isdecomposable to evolve a gas at a temperature higher than theevaporation temperature of said volatile organic solvent; and

(c) applying sufiicient heat to evaporate said volatile organic solvent,decompose said blowing agent and solidify said supercoating as apressure non-transferable porous layer having a thickness rangingbetween about 0.0025 mil. and 0.5 mil., and through which the ink of theink layer can be exuded under the effects of imaging pressure.

2. The process of claim 1 in which said dilute solution comprises fromabout 5% to about 20% by weight of said resin and from about 0.001 toabout 1% by weight of said blowing agent.

3. The process of claim 1 in which the synthetic resin of the ink layercomprises an acrylic resin and said dilute solution comprises a vinylacetate polymer.

4. The process of claim 1 in which the dried supercoating has athickness of from about 0.1 mil. to 0.3 mil.

5. The process of claim 1 in which the blowing agent is selected fromthe group consisting of p,p'-oxy-bis (benzene-sulfonyl hydrazide),N,N'-dimethyl-N,N-dinitroso terephthalamide, diazoaminobenzene, anddinitrosopentamethylene tetramine.

=6. Pressure-sensitive transfer elements produced according to theprocess of claim 1.

7. Pressure-sensitive transfer elements produced according to theprocess of claim 2.

8. Pressure-sensitive transfer elements produced according to theprocess of claim 3.

9. Pressure-sensitive transfer elements produced according to theprocess of claim 4.

10. Pressure-sensitive transfer elements produced according to theprocess of claim 5.

References Cited UNITED STATES PATENTS 1,962,082 6/ 1934 Miller 117-3642,313,645 9/ 1940 Antrim 11736.4 2,790,742 4/ 1957 Waart on 11736.42,803,579 8/1957 Stolle et a1 11736.4 3,080,954 3/1963 Neinman et a111736.4 3,104,980 9/ 1963 Maiersom 117-36.4 3,260,612 7/1966 Dulmage etal 117-36.2

MURRAY KATZ, Primary Examiner.

US. Cl. X.R.

